Association between childhood adoption & bad mental health: Not fully to be attributed to stressful environments; it is partly explained by differences in genetic risk between adoptees & those not-adopted

Childhood adoption and mental health in adulthood: The role of gene-environment correlations and interactions in the UK Biobank. Kelli Lehto et al. Biological Psychiatry, October 31 2019. https://doi.org/10.1016/j.biopsych.2019.10.016

Abstract
Background Being adopted early in life, an indicator of exposure to early life adversity, has been consistently associated with poor mental health outcomes in adulthood. Such associations have largely been attributed to stressful environments, e.g. exposure to trauma, abuse or neglect. However, mental health is substantially heritable, and genetic influences may contribute to the exposure to childhood adversity, resulting in potential genetic confounding of such associations.
Methods Here we explored associations between childhood adoption and mental health-related outcomes in mid-life in 243 797 UK Biobank participants (n adopted=3151). We used linkage disequilibrium score regression and polygenic risk scores for depressive symptoms, schizophrenia, neuroticism and subjective wellbeing to address potential genetic confounding (gene-environment correlations) and gene-environment interactions. As outcomes we explored depressive symptoms, bipolar disorder, neuroticism, loneliness, and mental health-related socioeconomic and psychosocial measures in adoptees compared to non-adopted participants.
Results Adoptees were slightly worse off on almost all mental, socioeconomic and psychosocial measures. Each standard deviation increase in polygenic risk for depressive symptoms, schizophrenia, and neuroticism was associated with 6%, 5%, and 6% increase in the odds of being adopted, respectively. Significant genetic correlations between adoption status and depressive symptoms, major depression, and schizophrenia were observed. No evidence for gene-environment interaction between genetic risk and adoption on mental health was found.
Conclusions The association between childhood adoption and mental health cannot fully be attributed to stressful environments, but is partly explained by differences in genetic risk between adoptees and those not-adopted (i.e. gene-environment correlation).

Keywords: gene-environment interplaydepressive symptomsschizophrenianeuroticismchildhood adversitypolygenic risk scores